Network planning of a cellular telecommunication network undergoes constant development due to increasing and/or changing capacity requirements and appearance of new structures affecting the coverage of cellular networks. Therefore, new cells or base stations are added to the cellular networks to increase the capacity and to provide improved coverage. Additionally, private base stations also known as home Node B's within the 3GPP (3rd Generation Partnership Project) have gathered extensive interest recently. A private base station may be considered as a personal base station exclusive to a single user or a group of users. On the network side, the private base station functions as a conventional base station in many ways except for the limitation to selected subscriber terminals the private base station is configured to serve.
Each cell is identified in the cellular network by a global or logical identifier which is unique to the base station in the whole mobile telecommunication network and by a physical layer cell identifier (PLCID) which is unique to the cell in a geographically limited area due to the limited number of available PLCIDs. If a base station provides service for only a single cell, the base station may be allocated a single PLCID. On the other hand, if a base station controls multiple cells, the base station may be allocated multiple PLCIDs (one for each cell). The PLCID is a signal sequence broadcast by the base station on a synchronization channel, and a mobile station identifies the base station from the signal sequence upon obtaining synchronization with the base station. In a long-term evolution (LTE) of Universal Mobile Telecommunication System (UMTS), the PLCID is a unique combination of one orthogonal sequence and one pseudo-random sequence, thereby resulting in a total number of 510 different PLCIDs and expected reuse of the PLCIDs in a cellular radio access network of UMTS LTE.
Neighboring cells or cells relatively close to each other should not use the same PLCID to prevent the mobile stations from acquiring synchronization with two base stations having the same PLCID, which would result in identity and interference problems severely disturbing the network operation. In conventional systems, a PLCID for a new cell to be added to the radio access network is derived from radio network planning information and preconfigured in a base station associated with the cell. Upon powering up the base station, the base station reads the PLCID from its memory, applies the PLCID, and broadcasts a signal sequence associated with the PLCID within the cell to enable mobile stations to identify the cell.
Preconfiguration of the PLCIDs to the base stations is, however, a cumbersome procedure which applies very poorly to the current networks with private base stations being established at random locations in the cellular network due to the unpredictability use characteristics of conventional users of the private base stations. For example, a given user may move his/her private base station to a location close to a public base station having the same PLCID as the private base station. This may result in identification problems and interference deteriorating the communication quality of both public and private base stations having the same PLCID. Therefore, a need exists not only to take into account the existence and unpredictable use of the private base stations but also to improve the flexibility of the PLCID allocation.